Generally, human eyes have higher visibility for low-frequency components than high-frequency components of an image. Therefore, in a case where noise of an image is reduced by using two-dimensional noise reduction (NR) with a small number of taps, low-frequency noise remains without being removed, and the noise is noticeable in some cases. On the other hand, if the number of taps of the NR is increased in order to reduce the low-frequency noise, a circuit scale and an arithmetic amount increase.
Therefore, it is conventionally suggested to reduce the image in a stepwise manner to reduce high-frequency noise of the reduced image at each step (refer to, for example, Patent Document 1). Specifically, the high-frequency noise of the reduced image approximates the low-frequency noise of the image before reduction. Therefore, by reducing the high-frequency noise from the reduced image, it is possible to obtain an effect substantially equivalent to that in a case of reducing the low-frequency noise of the original image. Also, since the high-frequency noise may be reduced by the NR with a small number of taps, it is possible to suppress an increase in circuit scale and arithmetic amount.